[unreadable] This is a renewal of a very successful project in which we have demonstrated that 3D MRSI data provided valuable information prostate cancer patients receiving External Beam Radiation Therapy (EBRT) and Brachytherapy. For patients that were scanned prior to therapy, we observed that the degree and spatial extent of elevated choline, reduced citrate and reduced polyamine correlated with pathologic tumor volume and grade, and that these parameters predicted short-term (_<1yr) response to therapy. For patients that were followed after therapy, we demonstrated that it was possible to detect the presence of biopsy proven prostate cancer after therapy based on elevated choline to creatine ratios and that "metabolic atrophy" occurred earlier than reductions in PSA. Of particular interest were the differences in the time course of changes in metabolite levels that we observed for EBRT versus Brachytherapy. The motivation for this project is to obtain longer follow-up and to study a larger patient population that is stratified for both risk and type of treatment. These are important issues because treatment failure normally occurs 3 to 10 years after radiation therapy and because there is considerable variability in the time course of response to therapy. This renewal will be a prospective MRI/MRSI study of patients prior to and serially after EBRT and Brachytherapy (HDR and PPI) in order to determine the prognostic value of the degree and spatial extent of the metabolic abnormalities. It will also test the hypotheses that; "metabolic atrophy" and elevated choline-to-creatine are early predictors of therapeutic outcome and that there are radiation dose dependent differences in the time course of metabolic response for EBRT versus Brachytherapy. Finally, ex-vivo HRMAS spectroscopy will be applied to biopsy samples of patients with biochemical failure to better define the metabolic profile of residual/recurrent cancer and its relationship with cellular proliferation and apoptosis. This is a translational project intended to provide new biochemical information about prostate cancer before and after radiation therapy and to aid in the translation of this technology into clinical practice. [unreadable] [unreadable]